If a giraffe's neck only has seven vertebrae, how is it so flexible? | HowStuffWorks If a giraffe's neck only has seven vertebrae, how is it so flexible? Anup Shah/ Getty Images Giraffes tower above all other mammals in the world. Loping along the African savannas on skinny, stiltlike legs, adult male giraffes can top out at 19 feet (6 meters) [source: National Geographic ]. But only around half of that height comes from their stems -- the rest is all neck. Then, if all of that length wasn't enough for these spotted giants, they have yet another tool to expand their reach. Giraffes' tongues can stretch as far as 18 inches (46 centimeters) to snag even the highest hanging leaf [source: San Diego Zoo ]. In regard to the long neck, scientists continue to scratch their heads about the exact evolutionary path the animal's ancestors took to instigate such a unique adaptation. One of the most compelling pieces of this puzzle is that the great expanse of neck contains a mere seven vertebrae. That's the same number of vertebrae that humans and almost all other mammals have.

From Jaws to Claws How do ducks float? For an explanation, many point to giraffes' preferred snack of acacia leaves, which would make the added extension necessary for craning to the tops of these 20-foot (6-meter) trees. However, giraffes also spend time, particularly during the later part of the day, with their legs splayed out, munching on grasses and low-lying shrubs [source: Dagg and Foster ]. Or perhaps it came about to impress the shorter-necked ladies. Giraffe males, called bulls, will duke it out in a neck-to-neck competition for female giraffes. Similar to rams locking horns in heated battles, the bulls use their hefty necks to strike each other with crushing force. Survival of the fittest would suggest that the ones with the longest and strongest would win. Whatever the case, those seven vertebrae dwarf the ones found in our bodies. In fact, each giraffe neck vertebra may be as long as 10 inches (25 centimeters) [source: San Diego Zoo ]. As you can guess, that doesn't exactly make for a light load to tote.

Stack up those seven blocks of bone and toss on a head, and we're talking around 600 pounds (272 kilograms) of cargo [source: San Diego Zoo ]. How do these lanky quadrupeds support their upper halves, much less move them around? Go on to the next page to find out the secrets inside nature's longest neck. ­ ­ Anatomy of a Giraffe - If a giraffe's neck only has seven vertebrae, how is it so flexible? | HowStuffWorks If a giraffe's neck only has seven vertebrae, how is it so flexible? Prev Next HowStuffWorks 2008 Certain characteristics of giraffe necks give them a flexibility rivaling any Slinky. The first feature is the way that the vertebrae in the neck, called the cervical vertebrae, are joined together. Remember that giraffes have seven of these bones, just like we do. However, giraffe cervical vertebrae are bound together with ball-and-socket joints [source: Owen ]. These are the kinds of joints that link your arm with your shoulder and offer a 360-degree range of motion.

Also, the joint between its neck and skull permits the giraffe to extend its head almost completely perpendicular to the ground. Moving down to where the neck meets the back, we find the second important anatomical feature for the giraffe's slinkiness. We call the vertebrae in the top portion of our backs the thoracic vertebrae. In humans, thoracic vertebrae are joined at the middle of the bone to provide added stability; and our cervical vertebrae fuse at the front and back for more mobility. Giraffe anatomy doesn't follow this same construction, and its first and second thoracic vertebrae are bound in the same way that its cervical ones are, with ball-and-socket joints [source: Dagg and Foster ]. That adaptation gives the giraffe an extra point of flexibility. It also accounts for the giraffe's signature hump [source: Encarta ]. Up Next Mountain Goat This highly flexible, yet heavy, body part is integral to the gangly animal's movement. Watch a giraffe and you'll notice that the neck moves back and forth with its stride. That's because the weight and motion of the neck guides the giraffe's center of gravity [source: Dagg and Foster ].

The animal also tosses its neck to and fro to help it rise to a standing position on its spindly legs. You can compare this to when we swing our arms up over our head to pull us out of bed in the morning. Strrreeetttcch! Manoj Shah/ Getty Images As another result of the long neck, a giraffe's blood has a long journey to travel. For that reason, the anatomy of a giraffe is quite amazing. The animal has a specialized cardiovascular system that keeps blood moving adequately to the brain and heart when it moves its neck and head around, ensuring that bending down to take a sip of water won't cause a possibly lethal head rush [source: Dagg and Foster ]. Giraffes' blood vessels are equipped with valves that prevent blood from backtracking due to gravity [source: Wood and Johansen ]. They also have a higher concentration of red blood cells , larger hearts and tighter skin, especially around their legs, which help circulate blood better [source: Dagg and Foster ]. Keeping everything chugging along, the giraffe also breathes at a relatively slow rate. Its enlarged lungs compensate for the trachea's extensive length, as the air travels up that long highway of a neck.

For more information about giraffes, visit the links on the next page. Giraffe | San Diego Zoo Animals & Plants San Diego Zoo Animals & Plants SPECIES: camelopardalis ABOUT Hello up there! Why do so many people look up to giraffes—besides the obvious reason? The long and short of it is that they are a wonderful example of nature’s creativity. Giraffes are the tallest land animals. A giraffe could look into a second-story window without even having to stand on its tiptoes! A giraffe's 6-foot (1.8-meter) neck weighs about 600 pounds (272 kilograms). The legs of a giraffe are also 6 feet (1.8 meters) long. The back legs look shorter than the front legs, but they are about the same length. A giraffe's heart is 2 feet (0.6 meters) long and weighs about 25 pounds (11 kilograms), and its lungs can hold 12 gallons (55 liters) of air! Its closest relative is the okapi. Giraffes have a small hump on their back and have a spotted pattern similar to that of a leopard.

For a long time people called the giraffe a “camel-leopard,” because they believed that it was a combination of a camel and a leopard. That's where the giraffe's species name camelopardalis comes from! Although a recent study of giraffe genetics published in the scientific journal Current Biology concluded that there are actually four distinct species of giraffes—said to be as different from each other as polar bears are from brown bears—one species is currently recognized, with nine subspecies. The subspecies have different coat patterns and live in different parts of Africa. Giraffe coat colors vary from light tan to practically black. The differences occur due to what the giraffes eat and where they live. Each individual giraffe’s markings are as individual as our fingerprints. Masai giraffes, from Kenya, have patterns that look like oak leaves. Uganda or Rothschild's giraffes sport large, brown splotches separated by thick, beige lines. The reticulated giraffe, found only in northern Kenya, has a dark coat with a seeming web of narrow white lines. Some researchers now believe that reticulated giraffes are so genetically different from the other subspecies that they should be reclassified as a separate species.

How many bones are there in a giraffe's neck? Just like humans, giraffes have seven neck vertebrae. For giraffes, however, each one can be over 10 inches (25.4 centimeters) long! Both male and female giraffes have two distinct, hair-covered horns called ossicones. Male giraffes use their horns to spar, throwing their neck against each other. As a male matures, calcium deposits begin to form on his skull to protect it when he head-butts with other males. These calcifications can be quite pronounced, giving the strange appearance of a three- to five-horned giraffe. Giraffes are so big that they really don't need to hide from predators. There is safety in numbers! It’s hard to pick out one giraffe from another when they form a tight group. Besides humans, only lions and crocodiles hunt them. If they have to, giraffes defend themselves with a deadly kick, karate-style. Their speed, the way they move, and their body designs also help them to escape predators if they need to.

Giraffes have a way of moving, or gait, in which both the front and back legs on one side move forward together, then the other two legs on the other side move forward. It’s called "pacing." Giraffes can run very fast—around 35 miles (56 kilometers) per hour for short distances. You might think watching out for lions and spending 16 to 20 hours a day eating would all weigh heavily on a giraffe. Surprisingly enough, giraffes only need 5 to 30 minutes of sleep in a 24-hour period! They often achieve that in quick naps that may last only a minute or two at a time. Giraffes can rest while standing, but they sometimes also lie down with their head resting on their rump. That’s a vulnerable position for a giraffe, though, so usually one herd member stays on guard. Many people think that giraffes have no voice, but they do make a variety of sounds, including moos, roars, snorts, hisses, and grunts. They just very rarely do so. One sound giraffes make when they’re alarmed is a snort.

Threats—such as lions nearby—may warrant a snort. Giraffes are often the early warning signal for other savanna animals: if a giraffe herd starts to run, everyone else does, too! Studies suggest giraffes vocalize below the level of human hearing and perhaps use this sound for long-distance communication. It’s easy to understand why giraffes top the list of so many people’s favorite animals. Their elegant stride, outrageous eyelashes, and calm expression give them an air of refinement. HABITAT AND DIET Blending right in: In a zoo, giraffes look conspicuous. But think of giraffes' presence in their African habitat, where their coat patterns actually serve as camouflage, blending with shadows and leaves. Giraffes are well adapted for living on the open, tree-dotted African plains. While other African herbivores compete for grass and small plants to eat, giraffes have the high branches with tender, young leaves all to themselves. It takes a lot of leaves to fuel such a large animal. Giraffes may eat up to 75 pounds (34 kilograms) of food per day.

They spend most of their day eating, because they get just a few leaves in each bite. Their favorite leaves are from acacia trees. These trees have long thorns that keep most animals from eating them. But those thorns don't stop the giraffes! They simply use their 18-inch (46-centimeter) tongue and prehensile lips to reach around the thorns. It is thought that the dark color of their tongue protects them from getting sunburned while reaching for leaves. Giraffes also have thick, sticky saliva that coats any thorns they might swallow. At the San Diego Zoo and the San Diego Zoo Safari Park, giraffes eat a variety of fresh acacia leaves hung high in artificial food “trees,” as well as hay, carrots, and low-starch, high-fiber biscuits. Giraffes are ruminants and have a stomach with four compartments that digests the leaves they eat. When giraffes aren't eating, they're chewing their cud. After giraffes swallow the leaves the first time, a ball of leaves travels all the way back up the throat into the mouth for more grinding.

Acacia leaves contain a lot of water, so giraffes can go a long time without drinking. When they do get thirsty, giraffes have to bend a long way down to drink from a lake or stream. When they're bent over, it is easier for a predator, like a crocodile, to grab hold of the giraffe. So, giraffes go to a watering hole together and take turns watching for predators. If water is easily available, like in zoos, they can drink 10 gallons (38 liters) a day. FAMILY LIFE When a giraffe baby, called a calf, is born, it comes into the world front feet first, followed by the head, neck, and shoulders. Its entry is like a slow-motion swan dive! Because the umbilical cord is only about 3 feet (1 meter) long, it breaks midway through the birth, allowing the newborn to drop to the ground. The fall and the landing don't hurt the calf, but they do cause it to take a big breath. The calf can stand up and walk after about an hour, and within a week, it starts to sample vegetation. Sometimes the mother leaves the calf alone for most of the day.

The youngster sits quietly until she returns. When a calf gets older, the mother leaves her youngster together with other calves in a "nursery." One of the moms stays to babysit while the others go out to eat and socialize. In the nursery, the calves develop physical and social skills through play. Under the watchful eye of the designated babysitter, the youngsters explore their surroundings throughout the day. The young giraffes can eat leaves at the age of four months, but continue to nurse until they are six to nine months old. AT THE ZOO Giraffes have drawn long looks from San Diego Zoo guests since 1938. Lofty and Patches were the Zoo’s first giraffes, arriving from Africa with much fanfare. Loading their crates off the ship and onto the truck for the long journey from New York to San Diego was quite a production, and upon their arrival here 10 days later, the giraffes refused to leave their traveling crate. Finally, someone offered them onions, and these veggies accomplished what nothing else could do. To this day, onions serve as a special treat for our giraffes!

The Zoo currently has a small herd of Masai giraffes that shares the exhibit in Urban Jungle with the much smaller Nubian Soemmering’s gazelles, adding interest for the animals and our guests. The Zoo has giraffe feeding opportunities. When you visit, be sure to check out the giraffe feeding times! The Safari Park is home to reticulated and Uganda giraffes; they share their field exhibits with a variety of antelope and rhinos, among other species, just as they might in the wild. Six-foot-tall (1.8 meters) feeding stations are ideal for giraffe calves—they can reach the food, but their antelope and rhino neighbors can’t. One of the Safari Park’s keepers says, “Telling the giraffes apart is like cloud watching. The longer you look at them, the more you’ll notice unique shapes in their spot pattern. And that’s how we tell them apart.” As the Safari Park has a large herd of Uganda giraffes (currently 16!), keepers photograph unusual characteristics of each one and keep the photos in a book in their keeper truck for easy reference.

Several years ago, it was suggested that, in their native ranges, many giraffe subspecies had begun to hybridize due to shrinking habitat—including the Uganda and reticulated subspecies, the two types we have at the Safari Park. Although some zoos chose to allow the two subspecies to crossbreed, we decided to keep ours separate. Now, the International Giraffe Group recommends not mixing the two subspecies; as Uganda giraffe populations dwindle, it’s important to preserve their genetic diversity in zoos. CONSERVATION In many African countries, giraffe populations are slowly decreasing because of habitat loss and the overgrazing of resources by livestock. As a result, the future of giraffes is dependent on the quality of the habitat that remains. Their numbers have decreased in the past century, and two giraffe subspecies, the West African or Nigerian giraffe Giraffa camelopardalis peralta and the Uganda or Rothschild’s giraffe G.c. rothschildi are endangered. While it has historically lived in western Kenya, Uganda, and southern Sudan, the Uganda giraffe has been almost totally eliminated from most of its former range and now survives in only a few small, isolated populations in Kenya and Uganda.

The Nigerian giraffe is found in just one area of Nigeria, and it is considered the rarest of the giraffes. The population of reticulated giraffes G.c. reticulata has dropped by an alarming 80 percent in just 10 years, most likely due to poaching. They are no match for humans with guns; giraffes are shot or snared for their meat, hide, bone marrow, and tail hair. The rest of the giraffe species have not become endangered for a number of reasons. Fortunately, Kenya is starting a giraffe conservation program for the three subspecies found there: reticulated, Uganda, and Masai giraffes G.c. tippelskirchi. San Diego Zoo Global supports a community conservation effort in northern Kenya that is finding ways for people and wildlife to live together. At the San Diego Zoo, we have a giraffe-feeding patio where high-fiber biscuits can be purchased and fed to the giraffes. The money raised through the sale of the giraffe biscuits funds the community conservation initiatives we support in Africa. You can help us bring giraffes back from the brink by supporting the San Diego Zoo Global Wildlife Conservancy .

Together we can save and protect wildlife around the globe. LIFE SPAN Freak of Nature: Sloth Has Rib-Cage Bones in Its Neck Freak of Nature: Sloth Has Rib-Cage Bones in Its Neck By Charles Q. Choi, Live Science Contributor | October 21, 2010 06:58am ET MORE These slow-moving mammals hang out in trees in tropical rainforests. A male three-toed sloth usually stays in the same tree for his entire life, while females move after giving birth, leaving her tree to the offspring, according to the WWF. Credit: Dreamstime. Unlike nearly every mammal that has seven vertebrae in its neck no matter how long or short its neck, sloths stand out as oddballs with up to 10. Now it turns out sloths are part of the fold (sort of) — what seem like extra neck vertebrae actually come from the rib cage. Scientists at the University of Cambridge in England and their colleagues investigated the development of mammal skeletons by using CT scans of fetal specimens from various species in museum collections from England, Germany, France, Australia and Switzerland.

Although birds and lizards show great variety in the number of vertebrae in their necks, with swans having twice as many as songbirds, the 5,000 or so species of mammals are far more conservative, generally possessing only seven neck or cervical vertebrae. In nearly all mammals, bone formation always takes place in the first few vertebrae of the rib cage before those of the neck. They found an exception was the three-toed sloth , which showed early bone formation in their lowermost neck vertebrae before those of the rib cage. However, closer analysis revealed that all mammals, including sloths, show early development of the eighth vertebra down from the head, whether or not it is part of the neck. In other words, the bottom neck vertebrae of sloths develop in a similar manner as the top rib cage vertebrae of other mammals. This suggests the lowermost neck vertebrae of sloths are developmentally the same as rib cage vertebrae of other mammals, but lack ribs. "The question was how on Earth does this animal do something so different from other mammals," researcher Robert Asher, a zoologist at the University of Cambridge, told LiveScience.

"The answer is that this sloth still actually has seven cervical vertebrae — it's just slid the ribs, shoulders and pelvis down the vertebral column a whole notch or two." This shows the structure of the mammalian neck is remarkably conservative after all, "even in those few species that superficially seem to be exceptions, like sloths," Asher added. "Even though they've got eight to 10 ribless vertebrae above the shoulders, unlike the seven of giraffes , humans and nearly every other species of mammal, those extra few are actually rib cage vertebrae masquerading as neck vertebrae." Asher noted that short-necked sloths possess five to six ribless neck vertebrae, while manatees typically have six. The researchers have a prediction regarding those anomalies as well. "They basically just put ribs on the bottom couple of neck vertebrae," Asher suggested.

"We plan to get a hold of some short-necked sloth and manatee specimens from museums to test our prediction." As to why sloths and manatees are such oddities when it comes to their necks and ribs, "a colleague of mine from Leiden University in the Netherlands named Frietson Galis suggests it could have something to do with the low metabolism rates one finds in both manatees and sloths," Asher said. A slower metabolism could blunt any side effects that might come with the mutations that might add body parts to necks, "including cancer," Asher explained."If you can't properly configure your neck to stop growing ribs, you probably can't stop cells from multiplying into tumors. Their low metabolisms might have helped them get around that problem." The scientists detailed their findings online Oct. 18 in the Proceedings of the National Academy of Sciences. Editor's Recommendations Giraffes – Necks for food or necks for sex? | WIRED Time of Publication: 12:24 pm. 12:24 pm Giraffes – Necks for food or necks for sex? The neck of a giraffe (Giraffa camelopardalis) is a marvelous thing.

Comprised of only seven vertebrae* – no more than in your neck – the towering feat of natural engineering is at once stunning and ridiculous. How could such a structure have evolved? This question is not just a throw-away. For the past century and a half, naturalists have been vexed by the long neck of the giraffe. *[This would not be a good science essay if I didn’t have to throw in some kind of caveat before I got out of the first paragraph. There is an ongoing anatomical debate about whether giraffes have only seven neck vertebrae or eight, the extra one being a modified part of the back. If you want to read up on the technical details of this hypothesis, see Nikos Solounias’ 1999 paper on giraffe anatomy .] As is traditional for big questions in evolution, the conundrum of the giraffe’s neck is often traced back to the work of Charles Darwin. Darwin, I was taught in my high school and college lectures, proposed that among an ancestral population of giraffes there were individuals which just happened to have slightly longer necks than their fellows.

This allowed them to reach higher branches, and as a consequence these giraffes were more reproductively successful since they persisted on an untouched food source while giraffes of lesser stature perished due to competition. (This simple trajectory was often accompanied by a cute little picture of a modern giraffe placed next to an ungainly “ancestral” species which was identical in all respects to its descendant except neck length.) It was a neat and simple equation – short-necked giraffes + natural selection + time = long-necked giraffes – but, like so many standard classroom tropes, it is also historically and biologically wrong. Even though the long neck of the giraffe would appear to be a stunning example of the power of natural selection, in the first edition of On the Origin of Species by Means of Natural Selection Darwin focused on a very different part of the mammal’s anatomy; it’s tail. The giraffe’s tail, although appearing to be “an organ of trifling importance”, was an excellent flyswatter which has probably played at least some role in helping individuals resist the attacks of biting insects.

From the beautiful intricacy of the vertebrate eye to the relative crudeness of the giraffe’s tail, natural selection could be consistently applied to explain the origins of adaptations. Darwin did not explicitly consider the neck of the giraffe until much later, and when he did it was as a response to one of his most serious critics. In 1871, the naturalist George Jackson Mivart published a book-length rebuttal to evolution by natural selection titled On the Genesis of Species. Like many other late 19th century naturalists, Mivart accepted evolution but rejected natural selection, and one of the major points of his book was that natural selection could not account for the intermediate stages between an ancestral and descendant form. According to Mivart, the giraffe was a perfect example of natural selection’s inefficacy. Assume that a giraffe’s long-neck truly was an adaptation for reaching high foliage during droughts which denuded other sources of food. This would be consistent with natural selection, Mivart argued, but if droughts truly had favored the lengthening of the giraffe’s neck then it is surprising that no other herbivores were adapted in the same way.

Likewise, the changes which must have occurred between the ancestral and modern giraffe must have extended beyond neck length alone. Various bits of anatomy and physiology would have had to have carried favorable variations in order for it to even be possible for giraffes to evolve long necks, and these changes – which would have increased the mass of the giraffe – would have required that it take in even more food under stressed, drought conditions. Mivart had set up a straw man argument, but Darwin took this criticism seriously. In the sixth, 1872 edition of On the Origin of Species Darwin responded at length to Mivart’s claims, and in the case of the giraffe he accepted Mivart’s scenario as a starting point. Given the competition which would have occurred among herbivores during times of drought, Darwin surmised, it is not surprising that giraffes can reach a level of vegetation that others cannot – competition would drive forms apart rather than keep multiple forms in close competition by adapting them in the same way. ( A.R. Wallace considered this same point over a decade earlier.) Nor were Mivart’s objections about variation and nutrition especially important.

Giraffes, like any other species, expressed variation, and the ability of individuals to reach food inaccessible to others would have led to the success of the taller forms. And, as far as drought conditions were concerned, Darwin countered that living giraffes were abundant in Africa. If the large, modern animals could survive temporarily stressed conditions, then why not intermediate forms which have since been replaced? Through accepting Mivart’s starting conditions, Darwin had presented a defense of his conception of evolution while also outlining a plausible pathway for giraffe evolution. What Darwin did not do was present a detailed, historical explanation for the form of the giraffe. Indeed, Darwin was typically careful in handling the history of life, and even when he was privately enthusiastic about fossil forms which exhibited transitional features – such as the feathered dinosaur Archaeopteryx – in his public works he avoided laying out precise step-by-step scenarios which would have taken place in the distant past. Darwin knew that paleontologists had only just begun to probe the fossil record, and so outlining phylogenies or tracing evolutionary lines of descent was a risky maneuver since those findings would almost certainly have to be revised.

The exchange between Mivart and Darwin did nothing to resolve the question of how giraffes had evolved. Proposing plausible adaptive scenarios was easy, but actually testing them has been another matter altogether. Even now, after nearly a century and a half since the exchange between Darwin and Mivart, the evolution of the giraffe’s peculiar neck remains contested, and the scope of the present debate has been shaped by two competing evolutionary hypotheses. The standard hypothesis, which is an extension of the argument Darwin outlined in 1872, is that competition for food drove the evolution of elongated necks. Through competition for nutritious browse, natural selection would have resulted in the evolution of a giraffe able to reach otherwise unexploited resources above the heads of other herbivores. The idea that giraffes gain such a benefit was supported by one of the few experimental studies to look at this question. As illustrated by Elissa Cameron and Johan du Toit in a 2007 study of giraffe feeding ecology, it was found that lower-level herbivores deplete the abundance and quality of browse available to giraffes.

By excluding browsers from feeding on certain Acaia trees, the scientists were able to measure just how much of a tree’s foliage competing herbivores scarf up, and it became apparent that giraffes would definitely get the most from each mouthful by browsing high when low- and mid-level browse had been cleared away. Giraffes can feed at a variety of levels, and this ability to reach high during times of tough competition certainly provides them with an advantage. The competing hypothesis is that giraffe necks evolved as a result of sexual selection. Even though naturalists have long-recognized that male giraffes often swing their necks to batter each other with their stout ossicones – Darwin even mentioned it in passing in Descent of Man – this habit was not thought to be especially relevant to giraffe evolution until a 1996 paper by Robert Simmons and Lue Scheepers entitled “Wining by a Neck: Sexual Seletion in the Evolution of Giraffe.” Citing the observation that many giraffes they observed fed at a lower level than they expected, Simmons and Scheepers argued that a long neck did not confer that much of a feeding advantage.

The competition between males, which they stated had longer and stronger necks, had driven the evolution of the giraffe neck, with female giraffes somehow carried along as sexual selection among males kept pushing the limits of neck length. The hypothesis proposed by Simmons and Scheepers has been controversial from the start and has received a good deal of criticism. One paper, published by G. Mitchell, S. J. van Sittert, and J. D. Skinner in the Journal of Zoology last year collected data suggesting that male giraffes do not energetically invest more in the growth in their necks than females do. In fact, not only did the necks of female giraffes continue growing through their lives, but they also added neck mass faster than males, and whatever differences there were between the necks of female and male giraffes appeared to be attributable to differences in overall body mass rather than the true sign of sexual selection. If the differences between living giraffes were so minimal, it seemed unlikely that males had truly driven the evolutionary change through sexual selection. Simmons and co-author R.

Altwegg have just responded to this study in a new Journal of Zoology paper, and in surveying the debate they state that neither the food competition nor the necks-for-sex hypothesis may be able to provide a comprehensive explanation for giraffe evolution. Although they dispute the findings of Mitchell, van Sittert, and Skinner – arguing that the data collected by the other team actually represents a significant disparity between males and females triggered by sexual selection – they rightly note that most of what has been said about giraffe necks has depended upon the anatomy and behavior of living animals. The arguments and experiments about the necks of living giraffes have more to do with the evolutionary pressures which are maintaining the form of the giraffe, but they may not be able to tell us very much about how long necks evolved in the first place. As identified by Simmons and Altwegg, the long neck of the giraffe may have evolved in response to some ecological change but then was co-opted into other functions which caused further alterations under different evolutionary pressures. The advantages provided by the giraffe’s long neck today – be it in terms of feeding, sexual selection, or both – cannot definitively tell us why the trait evolved in the first place.

The current function of a trait is not necessarily representative of why it evolved – an important caveat explicitly underlined by paleobiologists such as Stephen J. Gould and Elisabeth Vrba several decades ago. If the necks of modern giraffes are at least partially attributable to a shift in function, then our ability to answer the question of giraffe evolution cannot be based upon living animals alone. In order to test their preferred sexual selection idea Simmons and Altwegg suggest going back to the fossil record to see when giraffes evolved the blunt ossicones males use in their competitions and how this corresponds to neck length. If the evolution of blunt ossicones tracks neck elongation, they hypothesize, then this might be an indicator that head-swinging contests had something to do with the neck elongation (while the browsing hypothesis would have more to do with detecting a relationship between neck and leg length which would have pushed giraffes over the heads of competing browsers).

Correlation does not imply causation – even if the evolution of blunt, vertical ossicones and long necks coincided, that does not mean that the two are evolutionarily bound together – but by investigating these questions scientists would add a much-needed historical angle to research into giraffe necks. Unfortunately, fossil giraffes are not exactly a hot area of research, but recent work and forthcoming papers have the potential to provide a little more context to explain the origin of the giraffe’s impressive neck. Over the past several years it has been hinted that fossil giraffe expert Nikos Solounias has been describing the nearly-complete neck of a fossil giraffe called Bohlinia, a genus closely related to – if not ancestral to – the first members of the genus Giraffa. The full publication has yet to appear, but, as figured in Donald Prothero’s book Evolution: What the Fossils Say and Why it Matters , this specimen is intermediate in form between that of earlier, shorter-necked giraffes and the living giraffe. When compared to the greater swath of giraffe diversity, it may be a crucial part of detecting the pattern of giraffe neck evolution.

An outline of that pattern came out of a review published last year by N. Ludo Badlangana, Justin Adams, and Paul Manger. According to the known swath of fossil giraffes, significant neck elongation began around 14 million years ago during the Late Miocene – after the lineage to which the relatively short-necked okapi split off – and by about 5 million years ago giraffes of modern proportions had evolved. As bracketed between known fossil types, the transition between the early, short-necked forms and the first long-necked giraffes probably occurred between 14 and 12 million years ago, and if further discoveries bear this out then it appears that the elongation of giraffe necks occurred during a global pattern of aridification in which grasslands replaced forests. Again, this correlation does not by itself imply causation, but by investigating the tooth wear of giraffes before, during, and after this shift it could be detected whether their feeding habits changed and could have been part of the reason for neck elongation.

This, in turn, might provide some insight into the tempo of giraffe evolution – did their neck vertebrae slowly become elongated at a near-constant rate, or did the altered activity of regulatory genes cause faster, large-scale shifts which turned out to be advantageous in the altered habitat? Ultimately, a combination of natural history, embryology, and paleobiology will be needed to fully understand the unique anatomy of giraffes. This is not something which will be accomplished in a year or even ten, but will take the persistent investigations of many researchers working across a variety of scientific disciplines. For the moment, the question of “How did the giraffe get its long neck?” must be answered with “We do not yet know”, but that is as it should be. It is better to admit that we are still unraveling a mystery than to dogmatically assert that all is solved and that all the uncharted places on the evolutionary map have been filled in. Giraffes, just like every other organism alive today, have a long evolutionary history stretching back to the last common ancestor of all life on earth, but understanding how they were shaped over the span of Deep Time is an ongoing endeavor which is just as inspiring as it can be frustrating.

References: BADLANGANA, N., ADAMS, J., & MANGER, P. (2009). The giraffe cervical vertebral column: a heuristic example in understanding evolutionary processes?Zoological Journal of the Linnean Society, 155 (3), 736-757 DOI: 10.1111/j.1096-3642.2008.00458.x Cameron EZ, & du Toit JT (2007). Winning by a neck: tall giraffes avoid competing with shorter browsers. The American naturalist, 169 (1), 130-5 PMID: 17206591 Mitchell, G., van Sittert, S., & Skinner, J. (2009).

Sexual selection is not the origin of long necks in giraffes Journal of Zoology, 278 (4), 281-286 DOI: 10.1111/j.1469-7998.2009.00573.x Simmons, R., & Altwegg, R. (2010). Necks-for-sex or competing browsers? A critique of ideas on the evolution of giraffe Journal of Zoology, 282 (1), 6-12 DOI: 10.1111/j.1469-7998.2010.00711.x Simmons, R., & Scheepers, L. (1996).

Winning by a Neck: Sexual Selection in the Evolution of Giraffe The American Naturalist, 148 (5) DOI: 10.1086/285955 Cervical Vertebrae - Anatomy Pictures and Information Home > Skeletal System > Spine > Cervical Vertebrae Cervical Vertebrae The cervical vertebrae of the spine consist of seven bony rings that reside in the neck between the base of the skull and the thoracic vertebrae in the trunk. Among the vertebrae of the spinal column, the cervical vertebrae are the thinnest and most delicate bones. Yet, in spite of their size, the cervical vertebrae have the huge jobs of supporting the head, protecting the spinal cord, and providing mobility to the head and neck. The cervical vertebrae are stacked along the length of the neck to form a continuous column between the skull and the chest....

Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image 2D Interactive 3D Rotate & Zoom Change Anatomical System Vertebra and Spinal Cord, Cross-section Full Cervical Vertebrae Description [Continued from above] . . . Each cervical vertebra is named by its position in order from superior (C1 or first cervical vertebra) to inferior (C7 or seventh cervical vertebra). The C1 vertebra, which holds up the skull, is named the atlas after the mythological titan Atlas who similarly held the Earth on his shoulders. Similar to the C1 vertebra, the C2 vertebra is named the axis as it provides the axis upon which the skull and atlas rotate when the head is moved side to side. Each cervical vertebra consists of a thin ring of bone, or vertebral arch, surrounding the vertebral and transverse foramina. The vertebral foramen is a large opening in the center of the vertebra that provides space for the spinal cord and its meninges as they pass through the neck. Flanking the vertebral foramen on each side are the much smaller transverse foramina.

The transverse foramina surround the vertebral arteries and veins, which, along with the carotid arteries and jugular veins, have the vital job of carrying blood to and from the brain. Extending from the vertebral arch are several bony processes that are involved in muscle attachment and movement of the neck. The spinous process extends from the posterior end of the arch and serves as a connection point for the muscles that extend the neck, such as the trapezius and spinalis muscles. On the left and right lateral sides of each vertebra is a transverse process that forms the insertion point for the muscles of the erector spinae group that extend and flex the neck. A thickened region of bone known as the body lies anterior to the vertebral foramen and forms the main bone mass in all vertebrae except for the atlas. The bodies strengthen the vertebrae and support most of the weight of the tissues of the head and neck. Intervertebral disks made of rubbery fibrocartilage lie between the vertebral bodies to provide slight flexibility to the neck. Lateral to the vertebral bodies are flattened facets that form joints with the neighboring vertebrae and skull, allowing movement among the vertebrae.

The axis has a very distinct shape due to the presence of the odontoid process, a tooth-like prominence that extends from its body superiorly toward the axis. The odontoid process serves as the axis upon which the atlas rotates at the atlantoaxial joint. Despite being some of the smallest and lightest bones in the axial skeleton, the cervical vertebrae perform many important functions that are critical to the survival of the body. Vital nerves and blood vessels passing through the neck are protected from mechanical damage by the bony arches of the cervical vertebrae. The cervical vertebrae also provide support to the head and neck, including supporting the muscles that move this region of the body. The muscles that attach to the vertebral processes provide posture to the head and neck throughout the day and have the greatest endurance of all of the body’s muscles. Finally, the many joints formed between the skull and cervical vertebrae provide incredible flexibility that allows the head and neck to rotate, flex, and extend. Prepared by Tim Taylor, Anatomy and Physiology Instructor How many bones are in a giraffe's neck? | Reference.com How many bones are in a giraffe's neck? A: Quick Answer There are seven bones in a giraffe's neck.

A human neck has the same number of bones, though they are shorter. A male giraffe shows dominance by swinging its neck into the body of another giraffe. Full Answer Because of their lengthy necks, giraffes are able to feed off the leaves, fruits and flowers of tall trees. That reach is further extended by raising the head vertically upwards. Male giraffes can reach up to approximately 19 feet, which is about 3 feet higher than females can. A giraffe's foliage of choice is deciduous foliage during the rainy season and evergreen at other times.

Question: Man has seven vertebrae in his neck, how many does a Giraffe have?
Answer: Seven